Engines generally generate power by combusting a fuel. Chemical reactions taking place during combustion in the engine creates exhaust having multiple chemical compounds, in addition to generation of the power. The chemical compounds are exhausted from the engine into the environment. However, local governing bodies often regulate the exhaust of chemical compounds into the environment. For example, in the United States the Environmental Protection Agency (EPA) may regulate the release of certain chemicals into the environment.
Diesel engines generate nitrogen oxide (NOx) during combustion, which is released through an exhaust system of the diesel engine. NOx is monitored by the EPA, which places limits on the amount of NOx that may be exhausted into the environment. However, NOx is only one of several chemicals produced by engines, whether diesel or other, that is monitored and restricted. The amount of exhaust and chemicals released by an engine varies with the operating conditions of the engine. For example, the exhaust generated by an engine may vary with respect to the load placed on the engine.
Diesel engines are frequently used as power generators when connection to an electricity grid is unavailable or not functioning. For example, diesel generators may be used on ships and offshore platforms to generate power for ship-board and on-platform electrical devices. However, when used as a power generator, diesel engines may be subject to variable loads. FIG. 1 is a graph illustrating a load on a generator of a drilling rig rapidly changing over time. A line 102 of a graph 100 illustrates a load of a generator in kilowatts on a y-axis 110 versus time in seconds on an x-axis 112. When the load on the diesel engine rapidly changes, the exhaust generated by the diesel engine will also rapidly change.